Bandwidth-enhanced magnetoelectric antenna based on composite bulk acoustic resonators

Abstract

A bulk acoustic wave (BAW) driven magnetoelectric (ME) antenna has narrow operating bandwidth due to its high Q factor, and an effective mechanism for bandwidth enhancement is yet to be explored. This article presents a bandwidth-enhanced magnetoelectric (BWE-ME) antenna made of a Mo/AlN/FeGa sandwich stack, which is composed of three different resonant regions. These resonant regions in the discrete device can be equated as a parallel connection of dual high-overtone bulk acoustic resonators (HBARs) and single film bulk acoustic resonators (FBARs) with tiny frequency shift among the three resonators resulting in bandwidth broadening of the BWE-ME antenna. The resonant mode and return loss curves (S11) are simulated in a two-dimensional finite element method and fitted with the Mason equivalent circuit model. The frequency domain analysis shows that the magnetic flux density bandwidth generated by the multi-resonant mode interaction is 18 MHz, which matches the bandwidth of the measured reference gain S21 curve of the BWE-ME antenna, and the far-field radiated power characterization also shows the corresponding effective bandwidth distributed. The fabricated microelectromechanical systems antenna achieves a fractional bandwidth of 2.7% while maintaining the advantage of small size (0.49 mm2). Discrete composite BAW resonators that effectively combine the multi-resonant regions of HBARs and FBARs have the potential to realize compact and broadband BAW-ME antennas in the future.